The diversification in transparent conductive coating materials takes its source from the several issues related to indium tin oxide (ITO): limited indium supply on earth, high cost of the thin film deposition process, failing performances for applications demanding low surface resistivity, film flexibility and high transmission as well as toxicity of material. Thus, the critical trend in the current market of TCC is alternative technologies to ITO, which include carbon nanotubes, graphene, metal nanowires, other transparent oxides, conductive polymers, and conductive grids.
Some ITO-alternative technologies, like carbon nanotubes, graphene and conductive polymers can not provide sufficiently low sheet resistance or are too expensive to be considered for high volume production. Metal nanowires and nanoparticles have inherent problems with haze and transmission for materials with sheet resistance below <30 Ohm/sq.
The only viable alternative to ITO (and the only solution for large touch screen displays) is a conductive grid. Conductive grid (mostly made from metals, but other conductors are possible) has the capability to provide very low resistivity, approaching pure metal values, and at the same time keep optical transmission high, comparable with uncoated glass or polymer substrates. High transmission is an essential requirement for modern touch display devices. Also, since metal grid is fabricated by printing/patterning, this process can be integrated with trace patterning, which currently is responsible for more than 50% of touch screen production cost. The current grid based TCCs are prepared by deposition of the regular (periodical) grid of conductive bonds and could provide transmittance up to 90% at sheer resistance of 5-10 Ohm/sq.
It would therefore be desirable to have novel grid based transparent conductors with improved T/R performance as compared with TCCs made from regular conductive grids.